7.15pm update

Iran suspends sailor's release

British servicewoman Faye Turney (right) eating with her fellow British sailors in footage released by the Iranian government. Photograph: al-Alam/AFP/Getty

Tehran has suspended its plan to release the female sailor who is among the 15-strong British naval patrol that Iran's navy seized last week.

With the diplomatic deadlock showing no signs of breaking, Iranian officials blamed the UK's moves today to obtain a brief UN press statement, criticising the seizure of the Royal Navy team last Friday.

Tonight, the Iranian embassy in London released a second letter purportedly from the female captive, Leading Seaman Faye Turney, in which she called on Britain to start withdrawing its troops from Iraq.

"Isn't it time for us to start withdrawing our forces from Iraq and let them determine their own future?" she said in the letter, which was addressed to the British parliament and faxed to the Reuters news agency from the Iranian embassy.

Her first letter - which included a "confession" of entering Iranian waters - was released last night at the same time as Iranian television broadcast footage of her and her 14 male colleagues.

British officials are highly sceptical that she was speaking and writing of her own volition, and she looked strained in the footage.

Tonight, speaking before news of the second letter broke, Tony Blair was asked about last night's footage and said: "I just think it's completely wrong, a disgrace actually, when people are used in that way."

Mr Blair told ITV News that he did not want a confrontation with the Iranians but they must understand that the "only outcome" to the crisis is to release Britain's military personnel. Mr Blair added: "What we have to do in a very firm way, is step up the pressure."

Earlier tonight, Iranian television broadcast claims by an Iranian military official that global positioning system coordinates showed the British patrol was in Iranian waters.

Yesterday, the Ministry of Defence presented evidence from satellite technology that the patrol was 1.7 nautical miles inside Iraqi waters.

Part of the new footage from Iran also showed what it said was film of the operation detaining the British, Reuters reported.

It showed a Revolutionary Guards boat at sea closing in on what they said was a British vessel. One voice, apparently from the boat where the film was taken, shouts: "Are they British?" Another answers: "They are British, they are British."

The new film from Iran comes after the broadcast of footage last night showing the 15 captives, which prompted fury from the Foreign Office.

It had been hoped Leading Seaman Faye Turney, 26, would be released today after Iran's foreign minister, Manouchehr Mottaki, said yesterday that she would be freed soon.

But this afternoon, the Iranian military commander, Alireza Afshar, was quoted by an Iranian news agency saying her release "had been suspended".

Speaking earlier, Ali Larijani, the secretary of Iran's supreme national security council, said her release risked being delayed because the UK government had "miscalculated this issue".

He repeated warnings that Tehran would take legal action against the British personnel, who were held by the Iranian navy in an area near the mouth of the Shatt al-Arab waterway.

Mr Mottaki also said "admitting the mistake will facilitate a solution to the problem".

Today at the UN in New York, Britain asked the security council to support a brief press statement that would "deplore" Iran's detention of 15 British sailors and marines, and demand their immediate release, according to the Associated Press.

Some commentators doubt how strong the UK's hand is in the crisis and question whether the UK should involve the UN and potentially risk backing Iran into a diplomatic corner.

Britain has ignored Iran's threats about the UN, and a Foreign Office spokesman said today that the UK's ambassador, Sir Emyr Jones Parry, had been circulating a draft text among member states. "There will be a statement. We should hopefully get that later today," the FO spokesman said.

However, the press statement was likely to face problems from Russia and others because it reportedly says the Britons were "operating in Iraqi waters" - a point the Iranian government contests.

A press statement is the weakest action the security council can take, but the statement must still be approved by all 15 council members. Diplomats said Britain was also weighing a stronger presidential statement, which unlike a press statement, is read at a formal security council meeting and becomes part of its official record.

In the footage released by Iran last night, Leading Seaman Turney was shown "confessing" to a territorial transgression" but UK officials clearly believe she was not totally speaking of her own volition.

The first purported letter from Leading Seaman Turney was to her parents, saying she had "written ... to the Iranian people to apologise for us entering into their waters". Britain's ambassador to Tehran made an official complaint about the footage today.

Also today, the UN secretary general, Ban Ki-moon, met Mr Mottaki in Riyadh, where both are attending an Arab League summit. Mr Ban's spokeswoman said the detention of the British marines and sailors was one of the subjects they had discussed, but gave no further details.

In a further indication of heightened feelings, the Iranian consul in Basra today accused British forces of surrounding the consulate and firing into the air in a deliberately provocative act.

UK military officials in the southern Iraqi city denied the claims, saying the shots had come from a British convoy that was ambushed in the same street as the building.

There is evidence that the 15 British sailors and marines were captured and are being held by the Islamic Revolutionary Guard Corps, (IRGC) which represents a state within a state with its own forces, political representatives and hardline ideology.